Stannous fluoride reacts with tooth mineral to form Sn3F3PO4, although other products are possible under somewhat different experimental conditions: CaF2, SnHPO4. The rate of Sn3F3PO4 is to be studied experimentally as a function of the stannous and fluoride concentrations. Such information should be useful in the design of more effective topical preparations. BIBLIOGRAPHIC REFERENCES: K.G. Nelson and K.N. Amin, "Determination of Stability Constants of Stannous Fluoride Complexes by Potentiostatic Titration", J. Pharm. Sci., 64, 350 (1975). Mentioned last year as "in press".